1. Field of the Invention
The present invention relates generally to nuclear power plants and, more particularly, to a method of increasing the electrical power output of an existing nuclear power plant.
2. Description of the Related Art
Nuclear power plants may be of various configurations. One type of nuclear power plant employs a nuclear reactor to generate steam which is employed to turn one or more turbines that operate electrical generators. One type of reactor is a pressurized water reactor (PWR). Such a reactor operates by heating water within a primary cooling loop which is maintained at an elevated pressure. A steam generator, which can be characterized as a type of heat exchanger, thermally connects the primary cooling loop with a secondary cooling loop and generates steam in the secondary cooling loop. The secondary cooling loop is connected with the turbines and with a heat sink such as a cooling tower.
In most pressurized water nuclear reactors, a reactor core is comprised of a large number of elongated fuel assemblies. These fuel assemblies typically include a plurality of cylindrical fuel rods that are held in an organized array by a plurality of grids that are spaced axially along the fuel assembly length and are attached to a plurality of elongated thimble tubes of the fuel assembly. The thimble tubes typically receive control rods or instrumentation therein. Top and bottom nozzles on opposite ends of the fuel assembly are secured to the ends of the thimble tubes that extend slightly above and below the ends of the fuel rods.
A nuclear power plant can be said to include a nuclear island and a balance of plant. The nuclear island of a PWR generally includes a containment vessel, the reactor, the steam generator, a pressurizer, and a primary coolant pump, with the reactor, the steam generator, the pressurizer, and the primary coolant pump being disposed within an interior of the containment. A portion of the secondary cooling loop extends into the containment and is connected with the steam generator. The primary cooling loop carries thermal power away from the core to the steam generator, and the secondary cooling loop carries thermal power away from the steam generator to the balance of plant. The balance of plant would generally be stated as including those portions of the plant not included in the nuclear island, and it may be referred to herein as the BOP.
Nuclear power plants are licensed by the Nuclear Regulatory Commission to permit the generation of a certain amount of electrical power. It would be desirable to increase the amount of power that is generated by existing nuclear power plants in order to improve efficiency and to reduce the cost of power generation. However, a given nuclear power plant cannot be operated above its licensed power. Also, existing nuclear power plants generally are already being operated at their maximum capacity. While it would be desirable to enable the generation of additional amounts of electrical power, it would likewise be desirable to generate such additional electrical power with an environmentally friendly resource such as nuclear power without the necessity of building additional nuclear power plants.
It would be desirable, therefore, to provide an improved method of increasing the electrical power output of an existing nuclear power plant. Such an improved method may include the replacement of existing portions of the plant with equipment and/or components that are more efficient and/or that permit the generation of additional amounts of thermal or electrical power. Such an improved method may also include increasing the quantity of fissile material that is loaded into the core in order to increase the duration of the operation cycle of the reactor and/or to offset a reduction in the duration of the service interval that might result from increasing the power level of the reactor. Such an improved method might be such that the resulting improved plant could be relicensed at a higher power level. Such an improved method also might be such that the implementation or performance of the method does not require that the reactor be shut down for extended periods.